The blood-brain barrier (BBB) is a specialized system of capillary endothelial cells that inhibits certain substances in the blood stream from reaching the brain. While the BBB may protect the brain from harmful substances present in the blood stream, it may also prevent or severely delay the transport of therapeutic or diagnostic substances to the brain. Consequently, many drugs that are potentially useful for treating or diagnosing brain ailments cannot be administered through the blood because they cannot pass through the BBB.
Various techniques for delivering therapy to the brain thus begin with the opening of the BBB before administering a drug into the blood stream. One such technique uses ultrasound-induced cavitation to open the BBB. As the name suggests, ultrasound-induced cavitation is a process in which ultrasonic radiation causes bubbles to form and grow in a target region adjacent to where a drug is to be delivered through the BBB. The ultrasonic radiation is applied until the bubbles reach a condition that induces an opening in the BBB. Such ultrasound-induced cavitation events via transcranial exposure may have other therapeutic or diagnostic applications in the brain as well.
The foregoing technique involves focusing the ultrasound at the correct target region. Imaging techniques, such as magnetic-resonance imaging (MRI) or computed tomography (CT), are used to guide the ultrasound to the target tissue and to monitor the BBB. The opening of the BBB may be detected by evaluating MRI or CT images of the target region.